Converting bytes to KB, MB or GB means navigating between two counting systems that almost nobody clearly distinguishes. The factors of 1,000 (decimal) and 1,024 (binary) create differences that grow with each step. Understanding how this works helps avoid surprises when estimating a file’s size or a drive’s actual capacity.
Byte conversion table: KB, MB, GB and TB in decimal and binary
| Decimal unit (SI) | Symbol | Value in bytes | Binary unit (IEC) | Symbol | Value in bytes |
|---|---|---|---|---|---|
| Kilobyte | kB | 1 000 | Kibibyte | KiB | 1 024 |
| Megabyte | MB | 1 000 000 | Mebibyte | MiB | 1 048 576 |
| Gigabyte | GB | 1 000 000 000 | Gibibyte | GiB | 1 073 741 824 |
| Terabyte | TB | 1 000 000 000 000 | Tebibyte | TiB | 1 099 511 627 776 |
In decimal, each step multiplies by 1,000. In binary, each step multiplies by 1,024. The difference between the two systems reaches around 10% at the terabyte level, amounting to several dozen gigabytes on a high-capacity drive.
A byte conversion table for KB, MB and GB makes it easy to check these equivalents without working them out by hand.
Decimal and binary prefixes: why kB and KiB do not represent the same amount
The International System of Units (SI) assigns the prefix “kilo” a value of 1,000. Computing has long repurposed this prefix to mean 1,024 because memory operates in powers of 2. To remove the ambiguity, the International Electrotechnical Commission introduced binary prefixes: kibi, mebi, gibi and tebi.
In practical terms, kB means 1,000 bytes, while KiB means 1,024 bytes. The difference seems trivial at this scale, but it becomes significant beyond the gigabyte.
When to use each one
Ubuntu’s documentation policy recommends binary prefixes for file sizes and RAM, and decimal prefixes for disk capacities and network speeds. This reflects a simple principle: RAM is physically organized in powers of 2, while drive manufacturers measure capacity in multiples of 1,000.
- File size on disk or in RAM: the binary prefix (KiB, MiB, GiB) reflects how memory addresses are actually organized.
- Advertised capacity of an SSD or hard drive: the decimal prefix (kB, MB, GB) follows the convention used by manufacturers.
- Network speed: expressed in Mbit/s or MB/s, always in decimal, because telecommunications standards use SI units.
A conversion table that does not specify which base it uses is therefore mixing two systems. The result may seem consistent, but it leads to inaccurate calculations when dealing with large amounts of data.
Advertised and displayed storage space: understanding the difference
A drive sold with a capacity of 500 GB (decimal) really does contain 500 billion bytes. When an operating system divides that total by 1,024 at each step but still labels the result “GB,” it displays a lower figure. The same number of bytes appears smaller on screen, even though no storage space is actually missing.
This effect becomes more pronounced as drive capacity increases. On a drive advertised as 1 TB, the displayed difference amounts to several dozen apparent gigabytes.
Beyond the difference in units
The difference in displayed capacity is not the whole story. On Apple devices, the usable capacity is also reduced by file system formatting and the space occupied by the operating system. It is therefore important to distinguish between two sources of “lost” space:
- The purely mathematical difference between base 10 and base 2, which does not remove any actual bytes.
- The space used by formatting, metadata and the OS, which genuinely reduces the room available for user files.
To check the actual free space, use the file explorer rather than relying on a simple conversion calculation.
Typical file sizes: practical examples in KB, MB and GB
Units make more sense when compared with familiar items. A text document of a few pages usually takes up a few dozen KB. A photo taken with a recent smartphone uses several MB. A few minutes of high-definition video can take up several hundred MB or even exceed 1 GB.
These ballpark figures make it easy to estimate whether a file will fit on a USB drive or require a network transfer. They also help you assess how much storage you need: a drive with a few hundred GB is enough for documents and photos, while video collections or system backups call for capacities measured in TB.
Bits and bytes: a persistent source of confusion
A byte contains 8 bits. Network speeds are often expressed in megabits per second (Mbit/s), while file sizes are expressed in megabytes (MB). Dividing the advertised speed by 8 gives an estimate of how much data can be transferred each second. A speed of 100 Mbit/s therefore does not transfer 100 MB per second, but around 12.5 MB per second under ideal conditions.
The two differences (decimal/binary and bit/byte) add up in everyday use. Understanding them separately helps you avoid looking for a hardware problem when the only issue is a difference in convention. The table at the start of the article remains the most reliable starting point for calculations based on clear definitions.
